Automatic locking jack



April l7, 1945. J, MER|ER 2,373,773

AUTOMATIC LOCKING JACKS Filed Aug. 30, 1939 INVENTOR.

JE AN, MERCIER 3y his aZ-Zbrv zey I Patented Apr. 17, 1945 p UNITED STATES PATENT OFFICE I Aurom'rfj .IAoK I Jean Mercier, Neuilly-sur-Seine, France "Application August 30, 1939, Serial No. 292,639 I In France January 18, 1939 Claims (Cl. 121.40)

The present invention relates to hydraulic jacks.

The object of the invention is to provide a jack of this type with safety means for automatically locking the parts, that is to say, preventingthe discharge of the motive fluid, as long as .the external force to be resisted by the jack exceeds a given value.

Preferred embodiments of the present invention will be hereinafter described, with reference to the accompanying drawings given merely by way of example, and in which:

Fig. 1 is a longitudinal section of a jack, ac-

. cording to the present invention, as used for con trolling a retractable landing gear;

Fig. 2 isa diagrammatic view of a jack adapted to resist extension forces;

in'bothdirectionsby a shoulder 4a of body 4 and I a nut l3 screwed tothe open end of this body through which passes a rod rigid with slide-Valve 3'and projecting to the outside; these parts to and l3 being adapted to cooperate alternately with thelarger diameter of portion 3d of piston 3.

Fig. 3 is a view similar to Fig; 2 showing an other embodiment; I

Fig. 4 is a similar View showing a modification. In the embodiment shown by Fig. 1, the jackincludes a cylindrical body I and a piston 2 movable therein.

. In the embodiment of Fig. 1, the jack is suposed to control the operation of a retractable landing gear including a leg L carrying a wheel R. and pivoted to wing W. In order to be able to produce the pivoting of leg L with respect to wing W, the rod 2b of piston 2 is pivoted, at its end 2a to said leg L, while: a sliding member 3 carried by cylinder 1 is pivoted at 3ato' Wing W. Both pivots, preferably, include a certain amount of play. Thus, as lon a wheel'R is resting onthe ground, the weight of the aircraft tends to retract jack l-2.

Member 3 forms a slide-valve movable in a chamber formedin the head 4 of cylinder I,

said chamber being separated from said cylinder by the end wall 5'thereof. Slide valve 3 consists of a piston having three parts, 3b, 3c, 3d, of different diameters. Part 3b is provided in its pe-' riphery with an annular groove 5 adapted to connect the portions 1 and 8 of a conduit 9 which serves to supply or discharge fluid under pres.- sure to orfrom' said jack. Conduit 9lleads, in the embodiment shown in Fig, 1, into cylinder Preferably, a certain play is provided in the :bore of the nut l3 through'which portion 30 of There is also provided a small j part 3 passes. radial channel [4 in body 4 in the immediate vicinity of end 5 of cylinder I. This play and this channel permit the outflow of any fluid which may have been forced into the bore of hollow body 4 as a result of the displacements of part 3, and, thus, the movements of this part will not be impeded by a possible compression of such fluid. A conduit l5 opening into cylinder l in the vicinity of the end thereof, through which passes the rod of piston 2, serves, both, to supply a fluid under pressure to cylinder I in order to retract the jack: and to evacuate this fluid when fluid is being fed .to the other side of. the piston in order to expand the jack. j Y

- This jack works in the following manner: when the landing gear is retracted, the jack is also retracted and-piston 2 is near the end wall 5v of the cylinder. The fluid force entering through port l5 also forces cylinder l'away from the pivot point 3a, which in turn fcrces collar 3d against nut I3, also the spring I! holds groove 6 opposite portions l and 8 of pipe 9, which cor- 'nect portions! and 8 of pipe 9 with each other.

The landing gear is, thus, lowered and brought into the position shown by Fig. 1. In the event there was substantial resistance to the lowering I, at a, point ll located between piston 2 and end wall 5.

Preferably, there is provided a conduit 1 0 which branches off from coriduit'B, and also opens into cylinder I near the end 5 thereof. A check-valve I1. I The connection between portions I and 8 of pipe 9 is, then,cut off. Under these conditions, fluid can no longer be discharged from the jack since it cannot escape through'branch pipe ID, in

view of the presence of check valve I2, while the flow through 'I8 is cut on by the displacement of slide-valve'3. Therefore, while the action of the airplane weight on the jack tends to produce a discharge of fluid from the body of said jack, this action also displaces slide-valve 3 in such manner as to prevent said discharge.

As long as this weight is acting, that is to say, as long as the airplane is bearing on the ground, the jack cannot be retracted. On the contrary, as soon as the airplane has taken off, the air lift removes the weight on the landing gear and thus I member 3 is no longer forced inwardly by the weight of the airplane. Due to the play provided in pivots 2a, 3a and in the absence of anyload, spring I1 displaces member 3 outwardly. The jack can, then, be retracted by feeding fluid under pressure through conduit I5, since the fluid on the right hand side of piston 2 can escape through pipe 9, the portion I and 8 of which are now connected together through groove 6.

The jack shown by Fig. 2 is exactly similar to that of Fig. l, with the difference that it is adapted to operate by retracting, against the action of an external force F. The fluid under pressure is admitted through pipe 9 so as to move piston 2 inwardly with respect to body I, since pipe 9 opens at 2I, on the right hand side of said piston (while in Fig. 1 it opened at I I, at the left hand side of said piston). Pipe 20, with its check valve 22, plays the same part as pipe I0, with its check valve I2. Nut 23 plays the same part as nut I3 of Fig. 1. Spring 21 plays the same part as spring I! of Fig. 1, tending to hold slidevalve 3 in the position connecting together the portions I and 8 of pipe 9. The fluid force entering through port 2| tends to force the cylinder I in the direction of the arrows F acting against the force of spring 27. If the force becomes excessive, it will close the portions I and 3, while the force is still applied through the check valve 22 to the cylinder.

In the embodiment of Fig. 3 slide-valve 3 is subjected, both, to the action of an external force F and to the action of the fluid contained in the jack. The jack is similar to that shown in Figs. 1 and 2, with the exception that the bore formed in head 4 opens into cylinder I. Piston 3 is pro-,

vided with two stops as and 39 which limit its a check valve 32 opens at 5I into cylinder I. Another conduit 9 extends across head 4 and opens at 3I into cylinder I below the lower face of piston 2. According to whether itis desired to extend or to retract the jack, fluid under pressure is supplied through conduit 35 or through conduit 9, and is discharged through conduit 9 or through conduit 35, respectively. Piston 3 is provided with a bent conduit 52 extending from a point 53 on its cylindrical Wall to its inner end, so-as to connect conduit 35 with the inside of cylinder I when stop 38 is in contact with head 3. A groove 8 provided in piston 3 connects portions I and 8 of conduit 9 together when piston 3 is in this position. The fluid force entering from conduit, 35 tend to work against this spring 31 to close member 3, but the fluid enters through 5I, when fluid enters port 3| it tends to displace cylinder I in such a directionas to assist sprin The jack, according to Fig. 3 will work as follows:

It will be supposed thatthe parts are in the position shown by Fig. 3 (the external force F against which the jack is to act opposing inward displacement of piston 3, while piston 2 rests on a stationary part, for instance, the ground).

In order to extend the jack, fluid under pressure is supplied through conduit 35. This fluid passes through 30, lifts valve 32 and enters cylinder I at 5I When the pressure reaches a certain value in cylinder I, as piston 2 cannot move in said cylinder in view of discharge 9 being cut on. at I, piston 3 is driven outwardly. When stop 38of piston 3 has come into contact with head 4, the fluid under. pressure in conduit 35 can also flow through 53 and 53 into cylinder I; groove 5 possible.

afl'ords communication between portions 1 and 8 of conduit 9, so that the fluid contained in cylinder I. below piston 2 can be discharged through orifice 3I and conduits 9. Accordingly; the jack is extended.

If, at any time, the pressure drops in conduit 35 while an external .force, acting simultaneously in the direction of arrows F and F, tends to force both pistons 2 and 3 into cylinder I, then, piston 3 will move quicker inwardly with respect to said cylinder because its inward movement requires the expulsion of a much smaller amount of fluid than that of piston 2.

Immediately upon moving inwardly piston 3 outs off the flow of fluid through conduits 52 and i, and the jack is'locked in the position it occupies, since the fluid entrapped between head 4 and piston 2 cannot escape, as check valve 32 cuts off conduit 30.

In order to retract the jack, fluid under pressure is supplied through conduit 9. Since the fluid force enters by conduit 9, the discharge on the other side of the cylinder'must be through 53 and out conduit 35, while conduit 35 is connected to the discharge. This forces cylinder I in an opposite direction to the arrow F and assists spring 31 to position the member 3 so that fluid may bedischarged. 'I'hismovement of 3 and discharge is possible. only if piston 3 is in the position'in which stop 38 is applied against head 4. If a suflicient downward force (such, for instance, as a weight of an airplane) is exerted on piston 3, so that said piston is pushed back into the jack, the retraction of the jack is im- A spring 31 may be provided in order to keep piston 3 in the position in which the jack can be retracted except when the forces F, F exceed a given value.

An auxiliaryconduit 55 including a check valve 53 may be provided to permit the discharge of the ,small .amount of fluid which must be evacuthe locking position as long as the external force- (weight of the airplane) exceeds a predetermined value. j I When so used piston 3 will lock the jack, practically. until the wheels of the undercarriage have left the ground, and this structuraaccordingly, prevents a premature raising of theu'ndercarriage even in the event .of an erroneous operas:

tion of the controls by the pilot. a Fig. 4 shows 'a jack, according to the present invention, in which the distributing means 3, consisting, for instance, of an auxiliary piston is sub jected, both,- to the pressure of the fluid contained in the cylinder, and to the external forces illustrated by arrows F and F. which tend to pull thejack into an extended position; 1

In this embodiment auxiliary piston 3 extends across the end 4 of cylinder I in which it is axially slidable. The head 43 of piston 3 in cylinder i has a diameter practically equal to that of the head of piston 2. Portions l andB of conduit 9 can be interconnected by annular'groove'fi formed in the rod of piston 3. Preferably, a reaction spring 41 is interposed between the head 43 or part 3 and piston end 4." This spring urges part' 3 toward its 1 unlocking position, i. e., that in which groove 6 interconnects portions land 8 of conduit 9. In this position the fluid force entering port 4! tends to displace the cylinder 1 away from the pivot connection of member 3 thus closing the line 1-41, but the line 40 permits fluid pressure to pass check valve 42 and pass to cylinder I at 45, between head 4 thereof and head 43 of piston 3. The fluid. force entering port 45 will tend to force head 3 toward F and forcethe cylinder l toward F thus assisting the 1 spring 41.

. Head 43 of piston 3 is, preferably, mounted in cylinder l with a certain amount of play so that fluid can flow with a suitable resistance, from one side to the other of said piston head 43 to the surface of piston 2. The restricted space left between piston head 43 and cylinder l, and the strength of spring 41 should be carefully selected so as to insure the piston 3 being forced away from a locking position to prevent any risk of piston 3 coming back to the locking position while the jack is being extended as the ex-- haust fluid must pass through the conduitsl, El and 9. Piston 3 might be returned to the look;-

ing position under the force of the fluid admitted.

into the space between pistons 2 and 3' through conduit 45, thus preventing the escape of the exhaust fluid, but by providing a restrictor around the head 43, the fluid entering through 45 will build up against the restricted head forcing it toward F. When sufficient fluid has passed, the restricted head, it will force the piston 2 to an extended position.

The foregoing description is not intended to limit the present invention which extends to all changes, modifications, and equivalents within the scope of the appended claims.

Having now described my invention, what I claim as new and desire to secure by Letters Patent is:

1. A hydraulic jackfor use between two parts to produce relative displacement thereof; which comprises, in combination, liquid feed means and discharge means for said jack, and means, subjected to forces acting between'one of said parts and the jack, for cutting off said discharge means when an external force transmitted by at least one of said parts tends to deform the jack in the direction opposed'to that in which the liquid under pressure therein tendsto operate.'

2. A hydraulic jack for use between twoparts :to' produce relative displacement thereof, which comprises, in combination, liquid feed means and discharge means for said jack, means, subjected to forces acting between one. ofsaid parts and the jack, for cutting off saiddischarge means when an external force transmitted by at least one of'said parts tends todeform the jack in the direction opposed to that in which the liquid under pressure therein tends to operate, and

elastic means for urging said last mentioned means in the position thereof corresponding to the open position of said discharge means.

'3. A hydraulic jack for use between two parts to produce relativedisplacement thereof against an external force, which comprises, in combination, two'elements slidable with respect toeach other, by hydraulic pressure, liquid feed means and discharge means for said jack and valve means, movably carried by one of said elements, subjected to forces acting between one of said parts and the jack, for controlling said discharge means, adapted to produce the closing thereof when an external force transmitted by at least one of said parts tends to deform the jack in the direction opposedto that in which the liquid under pressure therein tends to operate.

4. A hydraulic jack for use between two parts to produce relative displacement'thereof against an external force, which comprises, in combination, two elements slidable with respectto each other, by'hydraulic pressure, liquid feed means and discharge means for said jack, valve means, movably carried by one of said elements, subjected to forces acting between one of said parts and the jack, for controlling said discharge means, adapted to produce the closing thereof when an ex ternal force transmitted by at least one of said parts tends to deform the jack in the direction 1 opposed to that in which the liquid under pressure therein tends to operate, and spring means interposed between said valve means and the jack element by which it is carried, for urging said valve means toward'the position thereof of corresponding to the open position of said discharge least one of said parts tends to deform the jack in the direction opposed to that in which the liquid under pressure therein tends to operate. 7

6. ,A hydraulic jack for use between two parts to produce relativedisplacement thereof which comprises, in combination two elements movable with respect to each other, to wit a cylinder and a piston movable therein, means for feeding a liquid underpressure into said jack on one side of said piston, a conduit opening into said cylinder on the same side of said piston, for the discharge of said liquid from said cylinder, and a slide valve carried by one of said elements so as to be movablewith respect thereto in the axial direction of said piston and said cylinder, subjected to forces acting between one of said parts and the jack, said slide valve being adapted to cut off said conduit when an external force transmitted by at least one of said parts tends to deform the jack in the direction opposed to that in which the liquid under pressure therein tends to operate. I

'7. A hydraulic jack for use between two parts to produce relative displacements, thereof which. comprises, in combination, two elements movable with respect to each other, to wit a cylinder and a piston movable therein, means for feeding a liquid under pressure into said cylinder on one side of said piston, said means including a feed conduit and a check valve in said conduit adapted to permit Only the flow of liquid therethrough toward said cylinder, a discharge conduit starting from the cylinder, n the same side of said piston as said first mentioned conduit, and a slide valve carried by one of said elements so as to be movable with respect thereto in the axial direction of said piston and said cylinder, subjected least one of said parts.

9. A hydraulic jack for use between two parts to produce relative displacement thereof, which comprises, in combination, two elements movable with respect to each other, to wit, a cylinder and a piston movable therein, means for feeding a liquid under pressure into said jack on one side of said piston, a conduitopening into said cylinder on the same side of said piston, for the discharge of said liquid from said cylinder, and a slide valve carried by one of said elements so as to be movable with respect thereto in the axial direction of said piston and said cylinder, subjected to forces acting between one of said parts and the jack, said slide valve forming a piston extending into said cylinder so as to be also subj ected to the action of the liquid pressure in said cylinder, said slide valve being adapted to cut oil said conduit when arr-external force transmitted by at least one of said parts tends to deform the jack in the direction opposed to that in which the liquid under pressure therein tends to operate.

10., A hydraulic jack for use between two parts to produce relative displacement thereof, which comprises, in combinatiomtwo elements movable with respect to each other, to wit, a cylinder and a main piston movable therein, means for feeding a liquid under pressure into said jack on one side of said piston, a'conduit opening into said cylinder on the same side of said piston, for the discharge of said liquid from said cylinder, and a slide valve carried by one of said elements so as to be movable with respect thereto in the axial direction of said piston and said cylinder, subjected to forces acting between one of said parts adapted to cut off said conduitwhen an external force transmitted by at least one of said parts tends to oppose the action of the jack thereon.

JEAN MERCIER. 

